Light blocking arrangement

ABSTRACT

A chamber with two normally transparent walls is arranged in the path of light. Injectors mounted on the wall of the chamber inject carbon to cover the transparent walls upon receipt of electromagnetic and light signals signifying a nuclear detonation.

United States Patent 1191 1111 3,709,584 Frungel I 1 Jan. 9, 1973 [54]LIGHT BLOCKING ARRANGEMENT OTHER PUBLICATIONS Inventor? Frank g b g,Germany Dickinson, H. & Tamarkin, P., Systems for the Detection andIdentification of Nuclear Explosions in the [73] Asslgnee' ImpulsphysikGmbH Hamburg Atmosphere and in Space. Proceedings of the IEEE,

Germany v01. 53 No. 12, December, 1965, pp. 1921-1934.

[22] Filed: Dec. 11, 1969 Marks, J. Carson, The Detection of NuclearExplopp No: 884,177 Nucleomcs. Vol. 17, No. 8, August 1959, pp.Champeny, J. C., et aL; Nuclear Bomb Alarm [30] Foreign ApplicationPriority D t Systems. Electronics, May 8, 1959, pp. 53-55.

Dec. 18, 1968 Germany ..P 18 15 249.3 Primary Examiner Ronald L. wibenAssistant Examiner-T. Major [52] US. Cl ..350/266, 250/2]? A"0meyMichae] Striker [51] Int. Cl .GOZI 1/30 [58] Field of Search ..350/266,267, 269; 343/100; 57 ABSTRACT 2 356/71 250/226 17 A chamber with twonormally transparent walls is arranged in the path of light. Injectorsmounted on the [56] References Cited wall of the chamber inject carbonto cover the trans- UNITED STATES PATENTS parent walls upon receipt ofelectromagnetic and light signals signifying a nuclear detonation.

3,321,630 5/1967 Durig et al ..250/226 X 3,342,540 9/1967 Abegg et al...350/267 14 Claims, 7 Drawing Figures 10 u l 1 l 9 a a a *Q, 3 Z 111T12:

23*" l 3 Z I :22

14 3 E 5 1/ 76 57 H R I PATENTEUJAH 9 I575 SHEET 2 [1F 2 INVENTOR FBAIICH4 F64,

ATTORNEY ucar BLOCKING ARRANGEMENT BACKGROUND OF THE INVENTION Thisinvention relates to a light blocking arrangement which blocks lightautomatically upon the occurrence of a nuclear detonation.

As a result of nuclear detonation, persons which are otherwise wellshielded may suffer eye damage or blindness. This may, for example,occur when soldiers in bunkers are in combat vehicles are visuallylinked to the outer world by means of observation equipment as forexample periscopes. Further, an atomic blast may also damage opticalequipment when the optical elements alone are exposed to the blast.

The present invention is based on the knowledge that a nucleardetonation results first in an electromagnetic impulse having a steepleading edge, followed within a short period of time by the light pulse,which also has a rapidly rising leading edge. Thus a sure sign of anuclear detonation which may cause optical damage is the appearance ofan electro-magnetic pulse having a predetermined leading edge slope,followed after a predetermined time interval by a light pulse having apredetermined light slope. Both the electro-magnetic slope and the lightslope resulting from such an explosion and the time interval between thetwo pulses are known data which were determined a long time ago. Thedate is furnished in the following discussion, as well as in a number ofreferences from which this data may be derived.

According to reference l, page 8, (R.W. Cottermann ElectromagneticDetection of Nuclear Weapons, Information Paper of ITT, (Unclassified),1965 by Robert W. Cottermann, Fort Wayne Laboratory, ITT CommunicationsSystems, Chicago, Illinois) the rise time ofthe EMP is less than I nanoseconds, with an accompanying field strength of IOV/m.

This data coincides with reference 2, FIG. 6.1 (Special InformationProducts Department, Defense Electronics Division Syracuse, N.Y.General'Electric, title: Nuclear yield measurement equipment.(Unclassified) from which a field strength of 2. IOV/m may be derivedfor a 0.1 KT explosion (the minimal explosion here postulated) at adistance of 0.2 km from ground zero.

Reference 3, (Propagation of the Ground Wave Electromagnetic Signal,with Particular Reference to a Pulse of Nuclear Origin" by J.R. .Iohler,proceedings of the IEEE December 1965, vol. 53, No. 12, page 2043) inFIG. 2 yields a field strength of 60/m at a distance of 44.6 km for anuclear detonation of medium strength.

Finally, reference 4 (Satellite-Based Detection of the ElectromagneticSignal from Low and Intermediate Altitude Nuclear Explosions by WilliamJ. Karzas and Richard Latter, Momorandum RM-4542 ofJune I965, of theRand Corporation) on page 5 furnishes a minimal field strength of morethan l0 1!" volts per meter, where d is in kilometers. This data is inclose agreement with that furnished in reference I for field strength ofIO V/m for the field near ground zero.

By the rules furnished herein for the decrease of the electromagneticpulse with distance, a minimal sensitivity for an EMP sensor of IO V/mfor a detonation taking place at a distance of I00 kilometers may bespecified, the sensor being adapted to detect a slope of at least l0V/musec during nano seconds. This value also agrees well with thatfurnished in reference 5,

(Nuclear Yield Measurement Equipment, Special Information ProductsDepartment, Defense Electronics Division, General Electric, Syracuse,N.Y.) wherein,

on page 5, file threshold value from instruments determining the yieldof nuclear bursts is stated to be between 5 to 50 volts per meter.

According to reference 1, page 4, an atomic explosion releases a certainsignal sequence with determined time intervals. The sequence alwayscommences with an initial gamma radiation and simultaneously with theelectromagnetic pulse. After a known time interval, the light flashfollows. When the time interval which is characteristic of the yield ofthe weapon is known, as well as the rate of rise of the optical flash,then, together with the above-mentioned characteristics of theelectromagnetic pulse, recognition of an atomic blast in a very earlystage may be achieved. The initial values of the slope of the lightflash may be derived from Glasstones, Effects of Nuclear Weapons I962edition, page 75. In conjunction with the Scaling Law" SUMMARY OF THEINVENTION In accordance with the above discussion, this inventioncomprises a light blocking arrangement for blocking light generated by anuclear detonation. The light is travelling along a determined path, andthe invention comprises blocking means arranged in said path and adaptedto block the passage of light along said path. It further compriseselectromagnetic sensing means for furnishing a first signalcorresponding to a received electromagnetic pulse. Also furnished areoptical sensing means for furnishing a second signal in response to areceived light pulse. Finally, circuit means are provided for furnishingthe activation signal for activating the blocking means in-response to afirst signal corresponding to an electromagnetic pulse having a leadingedge slope exceeding a predetermined electromagnetic leading edge slope,followed within a predetermined time interval by a second signalcorresponding to a light pulse having a leading edge slope exceeding apredetermined light slope, said light pulse further having a magnitudeexceeding a predetermined light magnitude.

In a preferred embodiment of the invention, the blocking means comprisea normally transparent chamber. The chamber has injector means forinjecting an opaque substance onto at least one wall of said chamber inresponse to the activation signal, thereby blocking the passage of lightalong said path. The opaque substance may, for example, be carbon orgraphite. The chamber may be in a housing which is joined to the housingcontaining the electrical circuits which furnish the activation signalonly when the previouslydefined signals are furnished by the optical andthe electromagnetic sensors. It is desirable that the injector chamberand the circuit housing be mechanically combined in a fashion in whichit is again easy to separate, in particular plug-in units are desirable.The activation signal may, forexample, be given by the circuit meanswhen the electromagnetic sensor senses a pulse of slope exceedings voltsper meter per microsecond while the optical sensor receives a lightpulse having a light slope of 3 Lux per microsecond after the timeinterval of between 5 microseconds and l millisecond.

The optical sensor may either be mounted directly within the injectionchamber or may be placed next to the injection chamber and connected viaa light conductor.

Furthermore, as a characteristic of the present invention, the injectionchamber may have a first and second thin, plastic-elastic transparentcover of limited elasticity.

The injectors may be mounted on the sides joining the edges of thetransparent plastic sheets. The injectors may be combined into a numberof groups, individual injectors belonging to different groupsalternating along the sides. In this case, the blocking arrangement maybe used a number of times, if a wiper for wiping the transparent sheetsis supplied.

It may be desirable to test the blocking arrangement of this invention.For this a special test signal generator may be supplied which has atransmitter which furnishes an electromagnetic pulse of more than 10V/m.us at a distance of 1000 meters, and is connected to a time delaymember which, after a time interval of 5 microseconds to l millisecond,generates an ignition pulse for a flash tube, which may for example beenergized by the discharge from a capacitor, said flash tube 7 beingable to generate a light pulse of a slope exceeding 3 Lux permicrosecond at the same distance.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a diagram showing thevariation with respect to time of the electromagnetic and the lightpulses;

FIG. 2 is a schematic top view of a blocking arrangement in accordancewith the present invention;

FIG. 3 is a section taken along line IIIIII of FIG. 2;

FIG. 4 is a block diagram of the circuit means of the present invention;

FIG. 4a shows the circuit diagram corresponding to the block diagram ofFIG. 4;

FIG. 5 is a block diagram of the transmitting unit for furnishing testsignals; and

FIG. 6 is a schematic sectional view of an injector.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of thepresent invention will now be described with reference to the drawing.

FIG. I is a schematic showing the effects of a nuclear detonation. It isassumed that the detonation takes place at time zero. At a determinedtime following time zero, namely at time r an electromagnetic pulse ofpredetermined slope appears. The slope should exceed 10 V/m.us. Afterfurther delay time of between 5 microseconds and l millisecond, at atime denoted by t a light pulse appears which should have a slope of 3Lux/us. At the beginning, the energy of the light pulse is still smalland only causes minimal damage. However the energy increases rapidly tocause the previouslymentioned damage. It is the object of the inventionto activate a blocking arrangement as fast as possible after time twhich blocks the light sufficiently rapidly that the high energy part ofthe light pulse is blocked. The time at which the blocking arrangementis activated, is indicated in FIG. 1 with t It is assumed that thearrangement blocks the light completely at the time indicated by t,.

The blocking arrangement illustrated in FIGS. 2 and 3 consists of twoparallel transparent thin sheets of limited elasticity, 1,2, withinjectors mounted at the sides joining the edges with a tight joint. Aninjector is shown in FIG. 6. Preferably, the injectors inject carbon. Inthe bottom of the injector, an ignition charge 4 with an initialexplosive charge of known composition, as for example lead acid, islocated. In the conical section above, graphite or carbon, preferablyxylol-carbon is located. The carbon charge 5 is covered with a thinsynthetic film 6 at its outer surface. The film may for example begenerated by hair spray. The activation of the injectors takes place inaccordance with the method described below by means of a condensordischarge of, for example, 40 Ws, which is obtained by charging acapacitor of 0.1 microfarads to a cor responding voltage and causing thecapacitor to be discharged at the correct time, namely time r of FIG. 1.

Between the two transparent sheets 1 and 2, which may be separated by adistance of 3.5 centimeters or more, is the actual injection chamber 7.A wiper 8 is mounted on one wall of the injection chamber, in such amanner that it is able to wipe the two inside surfaces of thetransparent sheets 1 and 2. Preferably, this wiper is manuallyactivated. On the side opposite to the wiper, a plug-in housing 9, whichwill be described in more detail below, is located. This contains theelectrical circuits of the blocking arrangement. The activation orignition signal for the injectors 3 is furnished via ignition lines 10and 10'. As may be noted with reference to FIG. 2, the injectors 3 arearranged in groups. The members of the group alternate around theperiphery of the chamber. This provides the possibility of using theblocking arrangement twice. If, for the first blocking operation, theactivation pulse is furnished via line 10, then only one-half of theinjectors 3 is activated. After the transparent sheets have beenblackened, the injection chamber may be cleaned by means of wiper 8, sothat the arrangement may be put into operating condition again, byfurnishing the next activation pulse via line 10'. The injectors arearranged in such a way, that the injectors on one side do not line updirectly with the injectors belonging to the same group on the otherside. Of course the possibility is also opened of using more than twogroups of injectors, with a correspondingly larger number of ignitionlines. In this manner, of course, the chamber may be used even more thantwice.

The speed of the injection depends upon the chemical structure.Experiment has shown that it is advantageous if for an optimum energytransmission between the injection charge and the carbon charge to beinjected, a small air cushion of, for example, l0 100 cubic millimetersis provided. This allows sufficient acceleration of the carbon thatblocking times of between 30-60 microseconds may be achieved,corresponding to an exit velocity of the carbon cloud of between 1500and 2000 meters per second. This velocity may be attained evenundernormal atmospheric pressure within the chamber, that is withoutnecessity of a vacuum.

FIG. 4 shows a block diagram of the electrical components of theblocking arrangement. An electromagnetic pulse is received by an antenna11 and furnished to the electromagnetic receiver 12. The output of theelectromagnetic receiver 12 is fed to an amplifier 13. This amplifier 13serves to limit the electromagnetic pulse, thus preventing excessiveenergy from penetrating to the following circuitry. Reception of thelight pulse is achieved by an optical sensor 15, which furnishes asignal to photoelectric transducing means 16. Unit 16 furnishes thesecond signal to a discriminator unit 14. This discriminator unit 14furnishes the activation signal, if a first signal corresponding to anelectromagnetic pulse of predetermined slope, has been furnished, and asecond signal corresponding to a light pulse of between 4000 and 6000 A,with a predetermined light slope, arrives within a predetermined timeinterval. As previously mentioned, the injectors 3 are ignited by meansof a condensor discharge. In FIG. 4, the numeral 18 indicates the blockwherein a number of ignition coils 19 are connected in series to form agroup. The ignition coils 19 of course are part of the injectors 3. Theignition coils 19 receive their energy from a capacitor 20, which mayfor example be charged to between 300 and 500 volts. The charging meansare denoted by 21. If the discriminator has determined that an atomicdetonation has taken place, then the activation signal is furnished tounit 17 which connects the charged capacitor 20 with the ignition coils19. A selector switch may be connected between the capacitor 20 and theignition coils 19 of two or more groups. This yields the capability tofire different injector groups in sequence.

FIG. 4a shows elements of the block diagram of FIG. 4 in greater detailand contains all electronic components in the above-explained sequence.Components 14,15,16, 17, 20 and 21, as shown in FIG. 4, are preferablylocated in a plug-in unit 9. The input of the unit 9 is connected vialine 22 to the output of amplifier 13. Further, of course, the housing 9must be supplied with the power sources required. From this unit 9, theinjectors 3 are supplied with energy via lines 10 and 10.

The photoelectric transducer housed in unit 9 may receive the lightpulse directly over a side of the injector chamber 7. However,preferably, it is connected via a photoconductor to sensor 15 and 15'which are directly with the injector chamber. If, as shown in FIG. 2,two optical sensors connected in parallel are used, the axes of majorsensitivity should diverge in order to allow a maximum coverage of thevisual field.

As shown in FIG. 4a, the electromagnetic pulse is furnished at R32 andis analyzed in a differential comparator stage. If a predeterminedpositive or negative threshold is exceeded, Q13 furnishes a triggerpulse. This pulse triggers monostable multivibrator M1, whose on" timeis determined by C18 and R40.

The output pulse of the multivibrator is differentiated and, after atime period determined by the on time of M1, a second monostablemultivibrator M2 is switched. The on time of the second multivibrator isdetermined by C19 and R41. During this on" time, two voltage comparators802 are switched to the ready state via lines strobe 1 and strobe 2. Inother words, as long as a voltage appears at strobe 1 and strobe 2, asignal arriving at the input of this stage causes the generation of anoutput pulse.

The tum-on level for stage 802 is determined by resistors R11 and R12,R13, R15, R16, and R18.

07 and 08 are normally on" switches. If they are opened simultaneously,C12 is charged over constant current generator Q9. After a predeterminedtime interval, dependent upon Q9, R24 and C12, Q10 is switched andcontrols the ignition of Q11, a solid state thyritron.

When Q11 becomes conductive as mentioned above, C 13 discharges, thusactivating the ignition of the injector.

The light pulse is received by photodiode Q1. Q2, Q3, Q4 and Q5 form acathode follower unit which, by means of feedback, decreases the inputcapacitance of O2 to a minimum. Operational amplifier 803 and Q6 serveto amplify the output of the cathode follower unit. The so-amplifiedoutput is then differentiated by C8 and R14 and integrated by theintegrating elements R17 and C9. Thus at the common point of C8 and R14,the voltage is proportional to the slope of the leading edge of thepulse, while the voltage at the common point of R17 and C9 isproportional to the total amount of light received during the pulse. Itcan thus be seen that the activation signal for the injectors, providedby the discharge of C13, only takes place when an output appears at bothstages labelled 802. This in turn is only possible when anelectromagnetic pulse having a predetermined leading edge slope isfollowed after a predetermined time interval by alight pulse also havinga slope exceeding a predetermined light slope and, further, having anamplitude exceeding a predetermined amplitude.

Since, surprisingly, the carbon to be injected shows hydroscopiccharacteristics, some exsiccator material is arranged in the chamber 7in order to counteract these tendencies. This exsiccator material may bearranged in the form of exchangeable cartridges. It is also possible toinclude this exsiccator material directly within the carbon injector 3.

In order to be able to test the above-described blocking arrangement, orto use this blocking arrangement during maneuvers, it is furthersuggested in accordance with this invention that special transmittingmeans be furnished, as illustrated schematically in FIG.

5. This includes a transmitter 24 which, upon activation of a releasekey 26, furnishes, via its antenna 25, an electromagnetic pulse of morethan 10 V/m us at a distance of 1000 meters. Connected with thistransmitter 24 are time delay means, 27, which generates time delaystarting with the activation of the release key 26. At the expiration ofthe time delay, an ignition pulse for flash tube 29 is furnished vialine 28. This flash tube is able to generate a pulse of more than 3Lux/us light slope at the above-mentioned distance. The time delay meansis so adjusted that the time delay furnished covers the range of between5 microseconds to 1 millisecond. The flash tube 29 may be equipped witha parabolic mirror 30 and is furnished energy from a condensor 31, whichin turn is charged by a unit 32.

While the invention has been illustrated and described as embodied inparticular circuits and particular blocking arrangements, it is notintended to be limited to the details shown, since various modifications, structural and circuit changes may be made without departing inany way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:

1. Light blocking arrangement for blocking light generated by a nucleardetonation and travelling along a determined path, comprising, incombination, blocking means arranged in the path of the light andadapted to block the passage of light along said path in response to anactivation signal; first sensing means for furnishing a first signalcorresponding to a received radio pulse; optical sensing means forfurnishing a second signal in response to a received light pulse; andcircuit means for furnishing said activation signal in response to athreshold first signal corresponding to a radio pulse having a leadingedge slope exceeding a predetermined radio leading edge slope, followedwithin a predetermined time interval by a threshold second signalcorresponding to a light pulse having a 7 leading edge slope exceeding apredetermined light slope and a magnitude exceeding a predeterminedlight magnitude.

2. An arrangement as set forth in claim 1, wherein said optical sensingmeans comprise a first and second optical sensor having respectively afirst and a second axis of maximum sensitivity, said first and secondoptical sensors being mounted in such a manner that said first axis ofmaximum sensitivity extends in a first direction and said second axis ofmaximum sensitivity extends in a second direction different from saidfirst direction; and means connecting said optical sensors in parallel.

3. An arrangement as set forth in claim 1, wherein said circuit meanscomprise first circuit means furnish ing a gating signal in response tosaid threshold first said activasignal; an second circuit mFansfurnishing l d d na an sai tion signs in the presence 0 said gating atthreshold second signal.

4. An arrangement as set forth in claim 1, wherein said first circuitmeans comprise means furnishing a first output signal in response to afirst signal having a leading edge slope exceeding 10 V/mus; meansdelaying said first output signal for substantially 5 microsecondsthereby furnishing a delayed first output signal; means for furnishing agating signal of substantially one millisecond width in response to saiddelayed first output signal.

5. An arrangement as set forth in claim 1, wherein said blocking meanscomprises a chamber having a first and second transparent plastic sheet,substantially parallel to one another; a first and second wallconnecting said first and second sheets and substantially perpendicularthereto; and further comprising a plurality of injectors for injectingan opaque substance arranged along said walls, each of said injectorscomprising a cartridge having an electrically ignitable injectioncharge. I

6. An arrangement as set forth in claim 5, wherein said injectors areelectrically connected to form a first and a second group, individualinjectors of the first group alternating in position with individualinjectors of the second group; further comprising wiper means for wipingsaid sheets attached to said first wall.

7. An arrangement as set forth in claim 1, wherein said predeterminedlight magnitude is 4000 A.

8. An arrangement as set forth in claim 5, wherein said opaque substanceis carbon.

9. An arrangement as set forth in claim 5, wherein said optical sensingmeans comprise an optical sensor mounted on said chamber; photoelectrictransducing means for furnishing said first signal; and light conductingmeans for interconnecting said optical sensor and said photoelectrictransducing means.

10. An arrangement as set forth in claim 5, wherein said circuit meansare mounted in a housing, said housing being plugably connected to saidchamber.

11. An arrangement as set forth in claim 5, wherein said opaquesubstance is xylol carbon.

12. An arrangement as set forth in claim 5, wherein said injectors havean injector charge and an air cushion between said injection charge andsaid opaque substance.

13. An arrangement as set forth in claim 12, wherein said chambersfurther contain exsiccator material; and cartridges containing saidexsiccator material.

14. An arrangement as set forth in claim 1, further comprising atransmitting unit for furnishing test signals for said light blockingarrangement, said transmitting unit comprising means for generating anelectromagnetic pulse of more than 10 V/m us, at a distance of 1000meters; time delay means for furnishing an ignition signal after a timedelay of from 5 microseconds to l millisecond following saidelectromagnetic pulse; and light flash generating means, responsive tosaid ignition signal for furnishing a light flash having a leading edgeslope of more than 3 Lux/us at the same distance.

' t t i i

1. Light blocking arrangement for blocking light generated by a nucleardetonation and travelling along a determined path, comprising, incombination, blocking means arranged in the path of the light andadapted to block the passage of light along said path in response to anactivation signal; first sensing means for furnishing a first signalcorresponding to a received radio pulse; optical sensing means forfurnishing a second signal in response to a received light pulse; andcircuit means for fuRnishing said activation signal in response to athreshold first signal corresponding to a radio pulse having a leadingedge slope exceeding a predetermined radio leading edge slope, followedwithin a predetermined time interval by a threshold second signalcorresponding to a light pulse having a leading edge slope exceeding apredetermined light slope and a magnitude exceeding a predeterminedlight magnitude.
 2. An arrangement as set forth in claim 1, wherein saidoptical sensing means comprise a first and second optical sensor havingrespectively a first and a second axis of maximum sensitivity, saidfirst and second optical sensors being mounted in such a manner thatsaid first axis of maximum sensitivity extends in a first direction andsaid second axis of maximum sensitivity extends in a second directiondifferent from said first direction; and means connecting said opticalsensors in parallel.
 3. An arrangement as set forth in claim 1, whereinsaid circuit means comprise first circuit means furnishing a gatingsignal in response to said threshold first signal; and second circuitmeans furnishing said activation signal in the presence of said gatingsignal and said threshold second signal.
 4. An arrangement as set forthin claim 1, wherein said first circuit means comprise means furnishing afirst output signal in response to a first signal having a leading edgeslope exceeding 10 V/mus; means delaying said first output signal forsubstantially 5 microseconds thereby furnishing a delayed first outputsignal; means for furnishing a gating signal of substantially onemillisecond width in response to said delayed first output signal.
 5. Anarrangement as set forth in claim 1, wherein said blocking meanscomprises a chamber having a first and second transparent plastic sheet,substantially parallel to one another; a first and second wallconnecting said first and second sheets and substantially perpendicularthereto; and further comprising a plurality of injectors for injectingan opaque substance arranged along said walls, each of said injectorscomprising a cartridge having an electrically ignitable injectioncharge.
 6. An arrangement as set forth in claim 5, wherein saidinjectors are electrically connected to form a first and a second group,individual injectors of the first group alternating in position withindividual injectors of the second group; further comprising wiper meansfor wiping said sheets attached to said first wall.
 7. An arrangement asset forth in claim 1, wherein said predetermined light magnitude is 4000A.
 8. An arrangement as set forth in claim 5, wherein said opaquesubstance is carbon.
 9. An arrangement as set forth in claim 5, whereinsaid optical sensing means comprise an optical sensor mounted on saidchamber; photoelectric transducing means for furnishing said firstsignal; and light conducting means for interconnecting said opticalsensor and said photoelectric transducing means.
 10. An arrangement asset forth in claim 5, wherein said circuit means are mounted in ahousing, said housing being plugably connected to said chamber.
 11. Anarrangement as set forth in claim 5, wherein said opaque substance isxylol carbon.
 12. An arrangement as set forth in claim 5, wherein saidinjectors have an injector charge and an air cushion between saidinjection charge and said opaque substance.
 13. An arrangement as setforth in claim 12, wherein said chambers further contain exsiccatormaterial; and cartridges containing said exsiccator material.
 14. Anarrangement as set forth in claim 1, further comprising a transmittingunit for furnishing test signals for said light blocking arrangement,said transmitting unit comprising means for generating anelectromagnetic pulse of more than 10 V/m us, at a distance of 1000meters; time delay means for furnishing an ignition signal after a timedelay of from 5 microseconds to 1 millisecond following saideleCtromagnetic pulse; and light flash generating means, responsive tosaid ignition signal for furnishing a light flash having a leading edgeslope of more than 3 Lux/us at the same distance.